The relative age effect refers to the performance-related advantage of being born early in a cohort or selection year. Until recently it was unknown whether the relative age effect generalizes across the lifespan. Medic, Starkes, and Young (2007) reasoned that the 5-year age categories that are widely used in masters-level sports to organize competitions and award prizes might be used to examine whether a relative age effect exists in older sports populations beyond the age of 35 years. Given the preliminary nature of Medic et al.'s (2007) results, along with their acknowledgment that those results "might not be generalizable to masters athletes from sports other than swimming and track and field or to masters athletes from countries other than the United States" (p. 1383), one purpose of this study was to determine if Medic et al.'s (2007) relative age effect findings can be replicated with world-class masters swimmers and track and field athletes from different countries. The second purpose of this study was to determine if a relative age effect exists in previously unexamined sports, such as masters weightlifting and rowing. The results of this study indicated that a relative age effect exists in masters swimming and track and field, but not in masters weightlifting and rowing, suggesting that this effect depends on the sport in which masters-level athletes compete. In particular, the authors' findings showed that the likelihood of participating in the world-level masters swimming competition is higher for individuals in the first year of an age category. (Contains 2 tables and 1 figure.)